1. Field
The present invention relates generally to the field of solid oxide fuel cell devices and, more particularly, to modular solid oxide fuel cell devices and methods for the use and operation thereof.
2. Technical Background
Solid Oxide Fuel Cells (SOFC) have been the subject of considerable research in recent years. While SOFCs can theoretically provide more efficient conversion of chemical energy from a fuel into electrical energy than conventional combustion engines, challenges remain in designing fuel cell systems that are stable for extended operational lifetimes.
The high temperatures associated with SOFC operation and the materials conventionally used in SOFCs present numerous challenges for design and operation.
Exemplary challenges include reduction of thermal shock during fuel cell startup and shutdown. Conventional SOFCs require extended startup schedules so as to uniformly and slowly heat the entire fuel cell stack prior to operation without creating excessive thermal stresses and component failures. Other exemplary challenges include control of the power output of a stack or fuel cell device and performance and/or lifetime limitations resulting from contamination or poisoning of a component, such as an anode, cathode or electrolyte surface. Such contaminants can originate from the fuel and/or oxidant gas streams or can be present in other fuel cell components. The presence of contaminants, such as, for example, hydrocarbons or sulfur, in a fuel gas stream can, in some operational modes, result in poisoning of the anode. Other contaminants can include components of glass seals and chromium containing compounds from device components. Chromium compounds are frequently present in metal components of a fuel cell system, such as frame materials, gas conduits, and electrical interconnects.
In conventional SOFC systems, performance loss occurring during fuel cell operation can frequently require that the entire fuel cell system be shut down and be at least partially disassembled and/or replaced, resulting in extra costs, delays and loss of power output. Removal of contaminants can often require disassembly and either cleaning or replacement of the contaminated components. The present invention addresses these and other concerns and challenges associated with the design of SOFC systems through, in part, a modular SOFC design and methods of operation that provide cyclic regeneration and activation of the SOFC electrodes.